The present invention pertains to automatically positioning a patient, who lies on a rest, such that the patient can assume an exactly predetermined posture and position particularly as far as certain body parts are concerned and in relation to particular equipment.
In particular, the invention relates to the automatic positioning of a patient so that a concrement in his/her body is placed into the focal point of a device provided for the comminution of such a concrement.
U.S. Pat. No. 3,942,531 corresponding to German printed patent application 23 51 247 describes a device including a focusing chamber for the comminution of concrements in the body of human beings. The focusing chamber is a portion of and pertains to a rotational ellipsoid that outlines and delineates the interior chamber wall. Such an ellipsoid has two focal points. Shock waves are produced through spark discharge at one of the focal points, and these shock waves are focused by the device in the second focal point. The chamber is filled with a liquid serving also as a coupling fluid to couple the body of the patient to the focusing chamber. The construction is chosen so that the concrement to be comminuted is situated in that second focal point of the ellipsoid. The shock waves are produced through an underwater arc discharge having two electrodes across which a capacitor discharges. As the discharge is ignited, shock waves are produced in the first mentioned focal point of the rotational ellipsoid. The ellipsoid is carefully constructed to permit a high concentration i.e. near pointlike concentration of shock waves in the second focal point. The pressure amplitudes may exceed 1 kbar and the duration of a shockwave pulse is less than 1 microsecond. A high concentration of shockwave energy is made possible on account of the high degree of focusing produced by the ellipsoid while on the other hand the shock waves as they converge towards the concrement and pass through normal tissue, affect that tissue only insignificantly. Following the destruction of the concrement and its pulverization or breaking up the concrement e.g. into grit, that grit will be discharged from the body by normal physiological process. This is particularly true in case of kidney stones.
It is of course apparent that the aforementioned method will function properly only if one knows exactly where that concrement is situated, so that in fact the device can be positioned such that the above mentioned second focal point coincides with that point in the interior of the body of the living being in which a concrement appears to have lodged. It is, therefore, necessary to determine the position of such a stone ahead of time i.e. prior to launching comminuting shockwaves. In the past one has used X-rays, particularly two separate X-ray beams, for obtaining spatial coordinate values of the concrement once the patient has assumed a particular position.
German patent 34 26 398 (see U.S. Pat. No. 4,936,291) describes a system by means of which a concrement is located, and the patient is positioned under utilization of a combination and, particularly, correlation of an X-ray locating system and an ultrasonic locating system. Here particularly the ultrasonic locating system will continuously monitor the position of the kidney stone, even after it has originally been located, and signals are provided and steps are taken to fix the location of the stone as far as external equipment is concerned.
It should be observed that when the patient is breathing the stone undergoes a certain movement and, therefore, may oscillate around a particular point at the rate of breathing. The second focal point of the rotational ellipsoid can be made to coincide with that particular zero point around which the kidney stone oscillates, and continuous observation of the stone as it moves and oscillates permits manual triggering of the shock waves right when the stone passes through the focal point. This is done through the ultrasonic system and only occasionally is the X-ray system used to determine the resolution and the extent any comminution of a kidney stone was successful. The automated or quasiautomated tracking and following of the equipment in relation to the kidney stone must require that it occurs in the ultrasonic section plane. Another locating device may be provided and shifting within the ultrasonic section plane may be made visible on a screen. One may locate and identify on a monitoring screen a kidney stone. The screen may simulate the ultrasonic section plane. Next, a light pen may be used on the screen to identify a particular point namely the point where the stone is located, and now computer operated functions may ensue.
The Munich Medical Weekly (Muenchner Medizinischen Wochenschrift, 125, 1983, No. 8, pages 151-155) describes a device for comminuting kidney stones through shock waves. The concrement is to be placed in the focal area of a bundled and focused shock wave. This position is obtained through a motor driven positioning device which is manually operated and controlled by the attending physician. Moreover, this device as described shows that the location of the stone is monitored by the physician through two independent X-ray systems.
German printed patent application 32 20 751 discloses a similar device which includes either two independent X-ray systems or two independent ultrasonic systems used in conjunction with a positioning device being independent from the foregoing equipment and operated by the physician. Further patents of interest are U.S. Pat. Nos. 4,669,483, 4,552,348, 4,938,232, Ser. No. 942,251 and U.S. Pat. No. 4,705,026.